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{{For|the Italian city with that nickname|Genoa}}
{{For|the Italian city with that nickname|Genoa}}
{{refimprove|date=July 2011}}
{{Starbox begin |
{{Starbox begin |
name = La Superba
name = La Superba
}}
}}
{{Starbox observe |
{{Starbox observe
epoch=[[J2000.0]] |
| epoch=[[J2000.0]]
constell=[[Canes Venatici]] |
| constell=[[Canes Venatici]]
| ra={{RA|12|45|07.83}}<ref name=hipparcos>{{cite journal|bibcode=2007A&A...474..653V}}</ref>
ra=12<sup>h</sup> 45<sup>m</sup> 07.83<sup>s</sup> |
dec=+45° 26' 24.92" |
| dec={{DEC|+45|26|24.92}}<ref name=hipparcos/>
| appmag_v=+4.86 to +7.32<ref name=gcvs>{{cite journal|bibcode=2009yCat....102025S}}</ref>
appmag_v=+4.8 to +6.3
}}
}}
{{Starbox astrometry |
{{Starbox astrometry |
| radial_v=15.30<ref>{{cite journal|bibcode=2006AstL...32..759G}}</ref>
prop_mo_ra=-2.20 |
| prop_mo_ra=-2.20<ref name=hipparcos/>
prop_mo_dec=13.05 |
| prop_mo_dec=13.05<ref name=hipparcos/>
parallax= 4.590|
| parallax= 3.12
dist_ly=711 ± 113 |
| p_error=0.34
dist_pc=218 ± 35
| parallax_footnote=<ref name=hipparcos/>
}}
}}
{{Starbox character
{{Starbox character
| class = C5<sub>4</sub>J, C-N5, C-J4.5
| class = C5<sub>4</sub>J(N3)<ref name=shenavrin>{{cite journal|bibcode=011ARep...55...31S}}</ref>
| b-v=2.54<ref name=ducati>{{cite journal|bibcode=2002yCat.2237....0D}}</ref>
| variable = Semi-regular
| u-b=6.62<ref name=ducati/>
| variable = [[Semiregular variable star|SRb]]<ref name=shenavrin/>
}}
}}
{{Starbox detail
{{Starbox detail
| age =
| age =
| metal =
| metal =
| mass = 3
| mass = 3{{cn}}
| radius = 215
| radius =
| rotation =
| rotation =
| luminosity = 5,800<ref name=ramstdedt>{{cite journal|bibcode=2014A&A...566A.145R}}</ref>
| luminosity = 4,400<br />(bolometric)
| temperature = 2,800 }}
| temperature = 2,600-3,200<ref name=neilson>{{cite journal|bibcode=2014A&A...568A..88N}}</ref>
}}
{{Starbox catalog |
{{Starbox catalog |
names=Y&nbsp;Canum Venaticorum, [[Harvard Revised catalogue|HR]]&nbsp;4846, [[Henry Draper Catalogue|HD]]&nbsp;110914, [[Bonner Durchmusterung|BD]]+46°1817, [[Fifth Fundamental Catalogue|FK5]]&nbsp;1327, [[Hipparcos catalogue|HIP]]&nbsp;62223, [[Smithsonian Astrophysical Observatory catalogue|SAO]]&nbsp;44317, GC&nbsp;17342
names=LA&nbsp;Superba<ref name=moore>{{cite book|doi=10.1007/978-1-84628-788-6_9}}</ref>, Y&nbsp;Canum Venaticorum, [[Harvard Revised catalogue|HR]]&nbsp;4846, [[Henry Draper Catalogue|HD]]&nbsp;110914, [[Bonner Durchmusterung|BD]]+46°1817, [[Fifth Fundamental Catalogue|FK5]]&nbsp;1327, [[Hipparcos catalogue|HIP]]&nbsp;62223, [[Smithsonian Astrophysical Observatory catalogue|SAO]]&nbsp;44317, [[Boss General Catalogue|GC]]&nbsp;17342
}}
{{Starbox reference
| Simbad = Y+CVn
}}
}}
{{Starbox end}}
{{Starbox end}}


'''La Superba''' (Y CVn, Y Canum Venaticorum) is a star in the [[constellation]] [[Canes Venatici]], well known for its strikingly red appearance.
'''La Superba''' (Y CVn, Y Canum Venaticorum) is a [[variable star|variable]] [[star]] in the [[constellation]] [[Canes Venatici]], well known for its strikingly red appearance.
[[File:Y Canum Venaticorum.jpg|thumb|right|Y CVn and simulation from [[Celestia]]]]
[[File:Y Canum Venaticorum.jpg|thumb|right|Y CVn and simulation from [[Celestia]]]]


⚫
==Appearance==
⚫
== Physical characteristics ==
La Superba is a [[semiregular variable]] star, varying by about a [[apparent magnitude|magnitude]] over a roughly 160-day cycle, but with slower variation over a larger range. Periods of 194 and 186 days have been suggested, with a resonance between the periods.<ref name=neilson/>


La Superba is a [[semiregular variable]] star, peaking at about +4.8 [[apparent magnitude|mag]] and diminishing to around +6.3 over a 160-day cycle. Known in short form as Y CVn, it is one of the reddest [[star]]s in the sky, and it is among the brightest of the giant red "[[carbon star]]s". It is the brightest [[Carbon star#The Revised Morgan-Keenan system|J-star]] in the sky, a very rare category of carbon stars that contain large amounts of [[carbon-13]] (carbon atoms with 7 [[neutrons]] instead of the usual 6). 19th century [[astronomer]] [[Angelo Secchi]], impressed with its beauty, gave the star its common name.<ref>[http://www.astro.uiuc.edu/~kaler/sow/lasuperba.html Jim Kaler: La Superba]</ref>
Y CVn is one of the reddest [[star]]s in the sky, and it is among the brightest of the giant red [[carbon star]]s. It is the brightest [[Carbon star#The Revised Morgan-Keenan system|J-star]] in the sky, a very rare category of carbon stars that contain large amounts of [[carbon-13]] (carbon atoms with 7 [[neutrons]] instead of the usual 6). The 19th century [[astronomer]] [[Angelo Secchi]], impressed with its beauty, gave the star its common name.<ref name=moore/>


⚫
==Physical properties==
⚫
La Superba's [[temperature]] is believed to be about 2800 [[Kelvin|K]], making it one of the coolest [[fusor (astronomy)|true stars]] known. Y CVn is almost never visible to the naked eye since most of its output is outside the visible spectrum. Yet, when [[infrared]] radiation is considered, Y CVn has a [[luminosity]] 4400 times that of the Sun, and its [[radius]] is approximately 2 [[Astronomical unit|AU]]. If it were placed at the position of the Sun, the star's surface would extend beyond the [[Planetary orbit|orbit]] of [[Mars]].
The angular diameter if La Superba has been measured at 13.81 [[mas]].<ref name=quirrenbach>{{cite journal|bibcode=1994A&A...285..541Q}}</ref> It is expected to be pulsating but this has not been seen in the measurements. At 320pc, this corresponds to a radius of 2.2 [[astronomical unit|AU]] ({{solar radius|473}}). If it were placed at the position of the Sun, the star's surface would extend beyond the [[Planetary orbit|orbit]] of [[Mars]].


⚫
La Superba's [[temperature]] is believed to be about 2800 [[Kelvin|K]], making it one of the coolest [[fusor (astronomy)|true stars]] known. It is faintly visible to the naked eye, and the red colour is very obvious in binoculars.<ref name=moore/> When [[infrared]] radiation is included, Y CVn has a [[luminosity]] several thousand times that of the Sun.
⚫
== Appearance ==


⚫
==Outlook==
⚫
To explain its remarkable coloration, it is necessary to understand that mid-sized stars, once they have finished [[Nuclear fusion|fusing]] [[hydrogen]] to [[helium]] in their core, begin to fuse [[Triple-alpha process|helium to carbon]]. During this so-called [[red giant]] stage, the outer layers expand and cool, causing the star's radiation output to move towards the red end of the [[electromagnetic spectrum]]. Near the end of the star's [[Stellar evolution|life cycle]], fusion products are moved outwards from the core by [[convection]], thus creating a [[carbon]] abundance in the outer atmosphere where [[carbon monoxide]] and other [[Chemical compound|compounds]] are formed. These [[molecule]]s tend to [[absorption spectrum|absorb]] radiation at shorter wavelengths, resulting in a remarkable [[spectrum]] with even less blue and violet compared to ordinary red giants, giving the star its distinguished red color.
After stars up to a few times the mass of the sun have finished [[Nuclear fusion|fusing]] [[hydrogen]] to [[helium]] in their core, they star to burn hydrogen in a shell outside a degenerate [[helium]] core, and expand dramatically into the [[red giant]] state. Once the core reaches a high enough temperature, it ignites violently in the [[helium flash]], which begins helium core burning on the [[horizontal branch]. Once even the core helium is exhausted, a degenerate carbon-oxygen core remains. Fusion continues in both hydrogen and helium shells at different depths in the star, and the star increases luminosity on the [[asymptotic giant branch]] (AGB). L Superba is currently an AGB star.


⚫
On the AGB, fusion products are moved outwards from the core by strong deep [[convection]] know as a [[dredge-up]], thus creating a [[carbon]] abundance in the outer atmosphere where [[carbon monoxide]] and other [[Chemical compound|compounds]] are formed. These [[molecule]]s tend to [[absorption spectrum|absorb]] radiation at shorter wavelengths, resulting in a remarkable [[spectrum]] with even less blue and violet compared to ordinary red giants, giving the star its distinguished red color.<ref name=abia>{{cite journal|bibcode=10.1086/342924}}</ref>
⚫
== Outlook ==


La Superba is most likely in the final stages of fusing its remaining secondary fuel (helium) into carbon and shedding its mass at the rate of about a million times that of the Sun's [[solar wind]]. It is also surrounded by a 2.5 [[light year]]-wide shell of previously ejected material, implying that at one point it must have been losing mass as much as 50 times faster than it is now. La Superba thus appears almost ready to eject its outer layers to form a [[planetary nebula]], leaving behind its core in the form of a vanishing [[white dwarf]].
La Superba is most likely in the final stages of fusing its remaining secondary fuel (helium) into carbon and shedding its mass at the rate of about a million times that of the Sun's [[solar wind]]. It is also surrounded by a 2.5 [[light year]]-wide shell of previously ejected material, implying that at one point it must have been losing mass as much as 50 times faster than it is now. La Superba thus appears almost ready to eject its outer layers to form a [[planetary nebula]], leaving behind its core in the form of a vanishing [[white dwarf]].<ref name=libert>{{cite journal|bibcode=2007MNRAS.380.1161L}}</ref>


== References ==
==References==
<references />
<references />


== External links ==
==External links==
* http://www.nckas.org/carbonstars/
* http://www.nckas.org/carbonstars/
* http://www.backyard-astro.com/deepsky/top100/11.html
* http://www.backyard-astro.com/deepsky/top100/11.html

Revision as of 15:53, 14 May 2015

For the Italian city with that nickname, see Genoa.
La Superba
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Canes Venatici
Right ascension 12h 45m 07.83s[1]
Declination +45° 26′ 24.92″[1]
Apparent magnitude (V) +4.86 to +7.32[2]
Astrometry
Radial velocity (Rv)15.30[3] km/s
Proper motion (μ) RA: -2.20[1] mas/yr
Dec.: 13.05[1] mas/yr
Parallax (π)3.12 ± 0.34 mas[1]
Distanceapprox. 1,000 ly
(approx. 320 pc)
Characteristics
Spectral type C54J(N3)[4]
U−B color index 6.62[5]
B−V color index 2.54[5]
Variable type SRb[4]
Details
Mass3[citation needed] M☉
Luminosity5,800[6] L☉
Temperature2,600-3,200[7] K
Other designations
LA Superba[8], Y Canum Venaticorum, HR 4846, HD 110914, BD+46°1817, FK5 1327, HIP 62223, SAO 44317, GC 17342
Database references
SIMBADdata

La Superba (Y CVn, Y Canum Venaticorum) is a variable star in the constellation Canes Venatici, well known for its strikingly red appearance.

Y CVn and simulation from Celestia

Appearance

La Superba is a semiregular variable star, varying by about a magnitude over a roughly 160-day cycle, but with slower variation over a larger range. Periods of 194 and 186 days have been suggested, with a resonance between the periods.[7]

Y CVn is one of the reddest stars in the sky, and it is among the brightest of the giant red carbon stars. It is the brightest J-star in the sky, a very rare category of carbon stars that contain large amounts of carbon-13 (carbon atoms with 7 neutrons instead of the usual 6). The 19th century astronomer Angelo Secchi, impressed with its beauty, gave the star its common name.[8]

Physical properties

The angular diameter if La Superba has been measured at 13.81 mas.[9] It is expected to be pulsating but this has not been seen in the measurements. At 320pc, this corresponds to a radius of 2.2 AU (473 R☉). If it were placed at the position of the Sun, the star's surface would extend beyond the orbit of Mars.

La Superba's temperature is believed to be about 2800 K, making it one of the coolest true stars known. It is faintly visible to the naked eye, and the red colour is very obvious in binoculars.[8] When infrared radiation is included, Y CVn has a luminosity several thousand times that of the Sun.

Outlook

After stars up to a few times the mass of the sun have finished fusing hydrogen to helium in their core, they star to burn hydrogen in a shell outside a degenerate helium core, and expand dramatically into the red giant state. Once the core reaches a high enough temperature, it ignites violently in the helium flash, which begins helium core burning on the [[horizontal branch]. Once even the core helium is exhausted, a degenerate carbon-oxygen core remains. Fusion continues in both hydrogen and helium shells at different depths in the star, and the star increases luminosity on the asymptotic giant branch (AGB). L Superba is currently an AGB star.

On the AGB, fusion products are moved outwards from the core by strong deep convection know as a dredge-up, thus creating a carbon abundance in the outer atmosphere where carbon monoxide and other compounds are formed. These molecules tend to absorb radiation at shorter wavelengths, resulting in a remarkable spectrum with even less blue and violet compared to ordinary red giants, giving the star its distinguished red color.[10]

La Superba is most likely in the final stages of fusing its remaining secondary fuel (helium) into carbon and shedding its mass at the rate of about a million times that of the Sun's solar wind. It is also surrounded by a 2.5 light year-wide shell of previously ejected material, implying that at one point it must have been losing mass as much as 50 times faster than it is now. La Superba thus appears almost ready to eject its outer layers to form a planetary nebula, leaving behind its core in the form of a vanishing white dwarf.[11]

References

  1. ^ a b c d e . Bibcode:2007A&A...474..653V. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  2. ^ . Bibcode:2009yCat....102025S. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  3. ^ . Bibcode:2006AstL...32..759G. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  4. ^ a b . Bibcode:011ARep...55...31S. {{cite journal}}: Check |bibcode= length (help); Cite journal requires |journal= (help); Missing or empty |title= (help)
  5. ^ a b . Bibcode:2002yCat.2237....0D. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  6. ^ . Bibcode:2014A&A...566A.145R. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  7. ^ a b . Bibcode:2014A&A...568A..88N. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  8. ^ a b c . doi:10.1007/978-1-84628-788-6_9. {{cite book}}: Missing or empty |title= (help)
  9. ^ . Bibcode:1994A&A...285..541Q. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  10. ^ . Bibcode:10.1086/342924. {{cite journal}}: Check |bibcode= length (help); Cite journal requires |journal= (help); Missing or empty |title= (help)
  11. ^ . Bibcode:2007MNRAS.380.1161L. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)

External links

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